Machine for flattening and curling of metal strip



Sept. 6, 1966 N. H. POLAKOWSKI MACHINE FOR FLATTENING AND CURLING 0F METAL STRIP Filed Aug. 17, 1964 Maia by fix is induced in the strip passing over the rolls.

United States Patent 3,270,543 MACHINE FOR FLATTENING AND CURLING 0F METAL STRIP Natalis H. Polakowski, Wilmette, IlL, assignor to The McKay Machine Company, Youngstown, Ohio, a-corporation of Ohio Filed Aug. 17, 1964, Ser. No. 390,167 11 Claims. (CI. 72162) This invention relates to a construction suitable for flattening of metal strip and for providing substantially flat metal strip which will spontaneously form into a coil, trough, or even a continuous tubular form, where desired. Although the invention is concerned primarily with the processing of thin and very thin metal strip, it can be advantageously applied to strips of intermediate and heavier gauges, such as from 0.015 to 0.04 inch.

Subsequent to cold working or heat-treating of metal strip, the strip often exhibits unsatisfactory flatness. This is an extremely undesirable situation since a high degree of flatness is required particularly where thin metal strip is to be used for the production of panels, boxes, cans and the like.

Lack of flatness characterized by edge or center waviness is attributed to dimensional inconsistencies across the strip width. Such inconsistencies arise during a rolling operation wherein certain strip sections are elongated to a slightly greater extent than adjoining sections. The dimensional differences which occur result in the lack of flatness while other undesirable characteristics are also prevalent by reason of variable internal stress patterns which result in an edgewise curvature or cam ber after slitting a wide band into narrow portions.

There are a wide variety of roller leveler constructions which are satisfactory for flattening strip above a certain thickness. In such roller levelers, the strip is exposed to alternating flexure between opposed sets of rollers arranged in a staggered relationship. Where a sufficiently high degree of flexure is provided, portions of the strip which are shorter than other portions will be slightly elongated and, as a result, buckles, waves, etc., can be removed. Accordingly, non-flat characteristics and undesirable internal stress patterns are not an insurmount able difliculty where relatively heavy gauge strip is involved.

It has been recognized, however, that flattening (leveling) of strips of about .012 inch or less in thickness, is diflicult, the degree of difficulty increasing rapidly with decreasing gauge. Wide strips of less than 0.007 inch thickness, particularly in the work hardened state, are almost impossible to flatten in a conventional roller leveler because suflicient plastic flexure cannot be accomplished.

The main difliculty with respect to such thin strip resides in the necessity for providing flexing rolls of sufficiently small diameter so that sufficient plastic strain It has been suggested that the ratio between strip thickness and roller diameter should be of the order of 1:100 or even 1:50 for efficient flattening. It will be apparent that where such ratios are involved, the rollers should be of the order of one inch in diameter or less for strip as thin as or thinner than 0.010 inch.

Flexing rollers as thin as those referred to have little inherent rigidity, and they tend to bend excessively over the discontinuous backing elements, such as are employed, in conventional leveler constructions. Where such bending occurs, suitable flattening cannot be accomplished, and streaks form in the surface of the strip. Consequently, roller levelers of orthodox design cannot use flexing rollers of a desired diameter, which is of the order of 0.75, 0.5 inch, or even less in diameter. In fact, the practical lower limit for flexing rolls in conventional full-width levelers is about one inch in diameter.

In applicants copending applications Serial No. 300,- 488 and Serial No. 356,530, of which this application is a continuation-in-part, there are described constructions which enable the use of thin flexing rolls whereby strip of extremely thin gauge can be suitably flattened. It is a general object of this invention to provide a further construction of the type described in these copending applications whereby thin gauge strip could be flattened without a large capital investment for new equipment being necessary.

It is an additional object of this invention to provide a mechanism for the flattening of metal strip which may utilize, at least in part, structural members which are already available in standard mill operations.

It is a still further object of this invention to provide a construction which produces flat metal strip having an inherent tendency to curl itself int-o a coil, trough-like or tubular shape upon leaving the flexing rolls thereby facilitating this operation if such is desired.

These and other objects of this invention will appear hereinafter, and for purposes of illustration, but not of limitation, specific embodiments of this invention are shown in the accompanying drawing in which:

FIGURE 1 comprises a schematic illustration of a leveler construction characterized by the features of this invention; and,

FIGURE 2 illustrates the construction in combination with a roller set which is used in conjunction with the leveler construction to control and/or suppress the spontaneous curling of the strip.

The leveler construction of this invention generally comprises a first set of flexing rolls which are disposed whereby the strip to be flattened can be moved through the apparatus in contact with the same side of each of the flexing rolls. The flexing rolls are adapted to be supported upon a large back-up roll, and this back-up roll may comprise .a large roll of the type used in existing rolling mill stands. It will be appreciated, therefore, that the leveler construction of this invention can be introduced into an existing mill by employing one roll of an unused mill thereby decreasing the amount of initial capital investment.

The construction also includes a set of deflector rolls which are disposed in alternating relationship with respect to the flexing rolls. The strip passes between the flexing rolls and the deflector rolls, and the flexing which occurs will introduce the necessary conditions whereby flattening will be achieved.

Support rolls are provided for movement in contact with the deflector rolls, and these support rolls are mounted in association with means constantly urging the support rolls into engagement with the deflector rolls. As will appear, the specific combination described permits the use of flexing rolls of extremely small diameter. Thus, the flexing rolls are maintained in position in the construction in a manner such that any tendency of the rolls to bend is resisted due to their contact with the large back-up roll, and due to the condition of the strip as it passes over the roll surfaces. In this latter connection, the deflector rolls bear on the strip in a manner such that forces are transmitted to the flexing rolls which are prevented from bending by the large back-up r-oll.

FIGURE 1 illustrates a large back-up roll 10 which, as indicated, may belong to the lower one-half of an unused rolling mill. A plurality of flexing rolls 12, 14, 16 and 18 are mounted for rotation in a manner whereby they bear against the surface of the roll 10. Deflector rolls 20, 22, 24, 26'and 28 are located in alternating fashion with respect to the flexing rolls, and strip 36 is guided so as to pass between the flexing rolls and the deflector rolls. It will be noted that one surface of the strip passes in engagement with each of the flexing rolls while the other surface of the strip passes in engagement with each of the deflector rolls. Roll 19 is essentially idle but it can also be driven, if desired, to relieve the tension from the takeup reel.

Support rolls 32, 34, 36, 38, 40 and 42 are operatively associated with the deflector rolls. These support rolls are journalled for rotation in members 44 and the particular journals may comprise pillow blocks or any conventional journal arrangement. The members 44 are each attached to a large support member or base 46, and force 48 is applied to 46 to constantly urge the support rollers into engagement with the deflector rollers. The pressure transmitted by the rigid base 46 is distributed substantially uniformly along each support and flexing roll. Suitable hydraulic, pneumatic or mechanical means may be employed for exerting the required force 48 upon the massive member 46. For instance, a conventional sc-rewdown mechanism (not shown) can be used for this purpose, the foot of the screws engaging 46 directly or via the upper work and/ or back-up roll.

It will be obvious that when the strip passes through the construction, it will be flexed to a degree dependent upon the diameter of the flexing rollers and the intermesh between the latter and the deflector rolls. Obviously, member 46 can be made to tilt for adjustment purposes or it can be stationary, the adjustment of the flattening device then being eflected by moving back-up roll is up and down.

In the illustrated embodiment, the rollers 12 through 18 are provided in successively increasing diameters. With this arrangement, the greatest degree of flexing will occur initially whereby the most pronounced stretching of the strip will be accomplished. The additional flexing operations then contribute in an additive but decreasing sense to the end effect achieved. In a typical example where low-carbon steel strip .002 inch thick is to be flattened, the roll 12 may be inch in diameter, the roll 14 may be /8 inch, the roll 16 may be /2 inch and the roll 18 may be inch.

The deflector rolls and their associated support rolls can also be employed in varying sizes, but their diameters will normally be much larger than those of the thinnest flexing rolls. Their particular size depends to a large extent on considerations involving inclusion of the rolls in the construction. Thus, smaller rolls may be necessary in certain areas due to the space available. In any event, the rolls must be selected whereby the desired bend is achieved as the strip passes over the flexing rolls.

It will also be noted that the arrangement illustrated provides a unique system for preventing bending of the flexing rolls during operation of the leveler. In the first place, the back-up roll provides a rigid support against which the flexing rolls bear whereby a high degree of resistance to 'bendnig is provided. Furthermore, the relatively rigid deflector rolls on either side of a flexing roll transmit forces from the strip to the support rolls and then to base 46 which resists any bending tendencies. Accordingly, very small flexing roll diameters can be used in this leveler and, therefore, very thin strips can be successfully processed.

The construction of this invention is particularly effective where the rollers engaging the strip are mounted with freedom for movement at their ends. With such an arrangement, the differential tension and resultant force components acting on each flex roll in a direction parallel to the surface of back-up roll 1!), pressure exerted by the strip on the rollers will not tend to bend the rollers as is the case Where rollers are fixed about an axis of rotation. Reference is made to the aforementioned copending applications for illustrations of the type of mounting contemplated for the flexing rollers. As noted in these cases,

the tension applied to the strip is effective to transmit pressure to the rollers for holding the rollers in an equilibrium position and the loose mounting at the roller ends prevents rubbing against holding plates at these ends when the equilibrium positions are assumed.

It has been determined that the strip processed in the device shown in FIGURE 1 will develop an inherent tendency to curl, the concave side of the strip facing the flexing rolls. This effect develops invariably when plastic, or elastic-plastic flexure is applied asymmetrically, i.e. the bending strain in one direction is larger than in the other. If a strip in this condition is pulled lengthwise, however, a transverse curvature of the same sign as the original longitudinal curvature appears, the strip acquiring the form of a continuous trough. The stronger the tendency for lengthwise curling, the deeper will be the said trough. In extreme conditions, e.g. when several small diameter flexing rolls are used in succession, the transverse curvature may reach the point where the two strip edges touch each other or even overlap, thus producing a continuous, open seam, thin Walled tube, which may be finished by welding, soldering, adhesive bonding or other methods.

Such a result is not always desirable, however, and the construction shown in FIGURE 2 provides a means for avoiding such curling. In this arrangement, the block 50 is intended to designate the construction of FIGURE 1. Preceeding this construction, there is provided an arrangement including deflect-or rolls 52, flexing roll 54, and backup roll 56. When the strip 30 is passed through this arrangement, it is flexed in a direction opposite the flexing accomplished in the construction 50. Accordingly, the curling tendency is offset, and strips suitable for longitudinal slitting pass out of the leveler. To achieve this end, it is recommended that roll 54 be of a smaller diameter than the smallest flexing roll in the main unit 5%.

Although the arrangement shown in FIGURE 1 involving the back-up roll 16 is preferred, it will be understood that more than one back-up roll could be employed, particularly in levelers employing additional flexing rolls. It will also be understood that the number of flexing rolls is not a limiting factor of this invention and all of these rolls could be of a same diameter if desired. Finally, reference to back-up rolls and support rollers in the appended claims is intended to refer to elements having cylindrical outer surfaces, such as rings, solid rolls and equivalent arrangements.

It will be understood that various changes and modifications may be made in the apparatus described which provide the characteristics of this invention without departing from the spirit thereof particularly as defined in the following claims.

That which is claimed is:

I. An apparatus for flattening and curling of metal strip comprising a set of flexing rolls, means for moving said strip through said apparatus whereby one surface of said strip passes through in engagement with said flexing rolls on one side thereof, a large back-up roll for said flexing rolls, said back-up roll engaging said flexing rolls on the opposite side thereof, a set of deflector rolls, each roll in said set of deflector rolls alternating with a roll in said set of flexing rolls, said deflector rolls engaging the opposite surface of said strip, and support rolls for engagement with said deflector rolls, and wherein the flexing rolls are mounted for free floating movement between the strip and the back-up roll.

2. An apparatus in accordance with claim 1 wherein means are provided for continuously urging said support rolls into engagement with said deflector rolls.

3. An apparatus in accordance with claim 1 wherein said flexing rolls progressively increase in diameter in the direction of movement of the strip through the apparatus.

4. An apparatus in accordance with claim 1 wherein the ratio of the diameter of the smallest flexing roll to the thickness of said strip is less than about :1.

5. An apparatus in accordance With claim 1 wherein said back-up roll comprises a roll mounted for free rotation in a roll stand.

6. An apparatus in accordance with claim 1 in which the axes of the deflector rolls are arranged in an arc approximating the curvature of the periphery of said backup roll.

7. An apparatus in accordance with claim 1 including additional flexing means associated with said apparatus for imparting a bending deformation to said strip of a sign opposite to the bend imparted by said flexing rolls whereby the tendency of said strip to curl upon passage out of said apparatus can be controlled.

8. An apparatus in accordance with claim 7 wherein said additional flexing means comprises a pair of deflector rolls, a flexing roll mounted for free floating movement intermediate said deflector rolls whereby one surface of said strip is adapted to pass in engagement with said deflector rolls while the other surface of said strip passes in engagement with said last mentioned flexing roll on one side thereof, and a large back-up roll engaging said last mentioned flexing roll on the opposite side thereof.

9. An apparatus in accordance with claim 8 wherein said additional flexing means is mounted adjacent the entrance end of said apparatus.

10. An apparatus as claimed in claim 7 in which the additional flexing means counteracts curl introduced by said flexing rolls to reduce the amount of curl.

11. An apparatus as claimed in claim 7 in which the deflector rolls are spaced one from another by an amount to enable the periphery of the flexing roll to overlap with the peripheries of the deflector rolls to cause flexing of the strip during passage therebetween.

References Cited by the Examiner UNITED STATES PATENTS 2,252,085 8/1941 Maussnest 72163 CHARLES W. LANHAM, Primary Examiner.

R. D. GREFE, Assistant Examiner. 

1. AN APPARATUS FOR FLATTENING AND CURLING OF METAL STRIP COMPRISING A SET OF FLEXING ROLLS, MEANS FOR MOVING SAID STRIP THROUGH SAID APPARATUS WHEREBY ONE SURFACE OF SAID STRIP PASSES THROUGH IN ENGAGEMENT WITH SAID FLEXING ROLLS ON ONE SIDE THEREOF, A LARGE BACK-UP ROLL FOR SAID FLEXING ROLLS, SAID BACK-UP ROLL ENGAGING SAID FLEXING ROLLS ON THE OPPOSITE SIDE THEREOF, A SET OF DEFLECTOR ROLLS, EACH ROLL IN SAID SET OF DEFLECTOR ROLLS ALTERNATING WITH A ROLL IN SAID SET OF FLEXING ROLLS, SAID DEFLECTOR ROLLS ENGAGING THE OPPOSITE SURFACE OF SAID STRIP, AND SUPPORT ROLLS ENGAGING THE OPPOSITE SAID DEFLECTOR ROLLS, AND WHEREIN THE FLEXING ROLLS ARE MOUNTED FOR FREE FLOATING MOVEMENT BETWEEN THE STRIP AND THE BACK-UP ROLL. 